Improvement in the processes of producing vitrified photo-enamels



UNITED STATES" PATENT OFFICE. 7

WILLIAM TINDILL WATSON, OF HULL, ENGLAND.

IMPROVEMENT IN THE PROCESSES 0F PRODUCING VITRIFIED PHOTO-ENAMELS.

Specification forming part of Letters Patent No. 153.732, dated August 4, 1874; application filed April 11, 1874.

To all whom it may concern:

Be it known that I, WILLIAM TINDILL WATSON, of Hull, in the county of Yorkshire, England, have invented an Improved Process for Producing Vitrified Photo-Enamels; and I hereby declare the following to be a full, clear, and. exact description of the same.

The negative to be employed in the production of a photo-enamel of the finest description, should be clear, sharp, and full of detail, but not too dense.

A transparent positive (so called) is required in the next place, which is made by the ordinary method of camera-printing on wet collodion. Any good bromo-iodized collodion will serve. The nitrate bath must be in good condition, as any trace of fog would be fatal to success, and a small stop must be used in the lens to insure sharp definition. The transparency is best developed with pyrogallic acid, three grains; citric acid, three grains; glacial acetic acid, twenty drops; water, one ounce.

A full exposure is required, varying from one or two minutes to a quarter of an hour, according to the density of the negative, light, 850. The development proceeds slowly, and the transparency when looked through ought to exhibit fine gradations of tone, from deep rich black to transparent glass in the high lights. Clear the picture with cyanide in preference to hypo, and wash quickly and well.

When a very dense negative is to be Worked from, it is often advisable to substitute iron development for the pyro.

For this purpose, ten grains of iron per ounce of water, with ten minims of glacial acetic acid may be used, but as the development in this case is very much more rapid it must be stopped by copious flooding with water as soon as the faintest indication of detail is observed in the face, 850., of the picture, which is now to be strengthened cautiously with a little of the pyro developer, to which a drop of silver solution has been added.

Removing the transparency from the glass is efi'ected by first cleaning off with the finger the extreme edge of the collodion all round the picture, and then placing it in a dish of water (say, half a pint) acidulated with twenty to thirty drops of sulphuric acid. In a few minutes the film, assisted by a gentle rocking motion of the dish, will loosen itself from the By the following method, however, a fine rich black is most easily obtained: Stock solution No. 1. Gold saturated solution of hichloride of iridium; Stock solutiou No. 2.- Ordinary chloride-of-gold solution, one grain to each dram of water.

The toning-bath is as follows: No. 1 solution of iridium, six drains; No. 2 solution of gold, three drams; water, six ounces. It is absolutely necessary that this bath be distinctly made, and with hydrochloric acid.

Immerse the picture and allow the toning to proceed until the proof in the densest parts has lost its original gray tint, and the whole appears of one uniform color. Examine the back of the picture through the glass, and note whether it is toned right through in the deep blacks. When the toning is finished, wash again in several changes of water, tak ing care to prevent the film from folding and creasing. With a little practice this is quite easy. Bear in mind that in all the operations hasty and rapid movements are to be avoided.

After washing, immerse for a few moments in the following bath, which serves to remove the chloride of silver formed during toning, and which if left in the image would impart to it a greenish tinge not all agreeable: Water, eight ounces; liquor ammonia, thirty drops. Then again wash very carefully in several changes of water.

If a fine black color is desired, the picture is now ready to be placed on the enamel-tablet and burned in; but if awarmer shade is desired, the picture is placed for two or three minutes in the following bath, observing not to allow it to remain atrest, but gently movty grains; water, eight ounces. Of each of these solutions, half a dram is taken and mixed with ten ounces of water and one minim of chloride-of-gold solution, to form the bath. A short immersion is suifieient to produce an appreciable warmth in the finished enamel. If left too long in this bath the picture is much reduced in depth, and in comparison is tame and feeble in its tones. After this, wash again the proof, and transfer it to the enamel-tablet.

To transfer the picture, you have only to place it in a shallow dish of pure water, with the glass on which it was taken underneath it. Let the glass down to the bottom of the dish, and slip the tablet between the film and glass, taking care that the collodion side of the picture is next the tablet. N ow lift carefully the glass bearing the tablet. Get the picture in its proper position on the tablet, and lift all out together gently, taking care that there are no creases or air-bubbles formed underneath the picture. Drain it, and dry smartly before a clear fire in an inclined position or over a spirit-lamp. When quite dry, out with a penknife the collodion film round the edge of the tablet, and remove from the glass. Place it on a sheet of blotting-paper, somewhere free from dust, to await the finishing operation of burning in. The part of the picture remaining on the glass may be utilized in a most excellent manner for retouching, should any be necessary, as follows: Dry it, and scrape it 0H the glass, and grind it up well with a little oil of lavender or spike on a pallet or a clean glass plate.

The burning in of the picture is as follows: The muffle-furnace having been charged with a mixture of coke and coal, and heated to a clear white heat, the picture is placed on a small piece of fire-clay, and allowed to remain on the top of the furnace for some time, so as to begin gradually to scorch off, as it were, the collodion film. It is necessary to use great caution here, as, if the temperature is raised too rapidly, the collodion film is liable to burst up and destroy the picture. The best way is to let it get thoroughly scorched brown all over before removing it (still resting on the piece of fire-clay) to the ledge in front of the mouth of the muffle. It is then to be introduced gently into the muffle by slow degrees, turning it round all the time with a stout piece of iron wire bent at the end, or by other means, and so complete the operation of burning off the collodion. When this is accomplished, and the whites of the picture appear clear, it is withdrawn gradually, and placed on the furnace top to cool somewhat; and the rest of the enamels may then be treated in the same manner, after which they are placed in a suitable situation to become thoroughly cooled, when they are ready to be glazed. If

any spots, however, appear, they are to be retouched with the pigment, before described, ground up with a little oil of lavender, and then placed again for a few seconds in the muffle, observing the same precautions in grad ually introducing and withdrawing it.

The glazing is performed as follows: Take a teaspoonful of soft transparent enamelglaze, such as is used for glazing fine porcelain, mix it with a little water, and grind it well on a glass slab with a glassmuller. Let it dry, and then put it in a bottle with one oun'ceof alcohol, shake it up well, and allow the heavy particles to subside for a moment or two. Pour off the top into a clean glass measure, and add to it three ounces of plain uniodized collodion previously thinned, and shake well.

This forms the glaze, which is applied to the picture in the same manner as coating a plate of glass with collodion. Have ready a piece of very bibulous paper, and. apply it to that edge at which the superfluous collodion was poured off, so as to remove the thick edge of collodion that is otherwise formed. Allow it to become quite dry, and your furnace being still at a white heat, introduce the picture as before when burning off the collodion by slow degrees into the mufie,'and when the glaze appears to be melted, the picture is withdrawn to cool as before.

It frequently happens that this process of glazing has to be repeated three times or more,

according to the density of the blacks of the picture, which will otherwise retain their orig inal dead-matt appearance, and will not be properly transparent. When, however, the picture is thoroughly glazed, the deepest blacks appear translucent, and the finished result is of the most beautifuldescription imaginable.

The method known as Grimes method of toning with platinum has been extensively used, and with very varying results. proofs, however obtained with platinum toning, are not to be compared with those secured by the modified iridium toning-bath in intensity and depth of coloring.

It is remarkable that iridium, if used alone as a toning agent, is tardy in its action, and almost unmanageable, and only produces a poor result; and that gold toning alone forms a dirty reddish image when burned, entirely deficient in half-tone; but when the two are combined in the proportions indicated, a most beautiful and intense black is formed.

The toning bath possesses good keeping qualities, and may be used many times by simply adding a little of the iridium and gold solutions in the proper proportions.

Should the enamel after glazing require any retouching, it may be easily performed by taking some of the pigment previously described, and grinding it with a minute portion of the powder glaze or flux with oil of lavender, and then submitting it again to the action of the furnace until the retouching appears bright, like the rest of the picture.

The

In all the burnings it is recommended to 6X amine the picture often until facility is acquired, as, if the heat is great and too long continued, the white-enamel ground may begin to melt and flow and destroy the picture. A very little careful practice in this matter is sufficient, however, toinsure proficiency.

What I claim as my invention, and desire to secure by Letters Patent, is

1. The process herein described for producing vitrified photo enamels, substantially as and for the purpose set forth. 7

2. In a toning-bath for use in producing vitrified photo-enamels, the combination of a salt of iridium and a salt of gold, in about the proportions and for the purpose substantially as set forth. t I

3. A glazing composition for vitrified photoenamels, consisting of an ordinary glazing compound, alcohol, and plain uniodized collodion, combined as described, and for the purpose substantially as set forth.

Witness my hand this 5th day of February, A. D. 1874.. p

WILLIAM TINDILL WATSON. In presenceof- JAMES HAREBOOTH GRESHAM,

Solicitor, Hull. Tnos. 000K,

Chief Constable of Hull. 

